Pharmacokinetics of cannabidiol in a randomized crossover trial in senior horses

OBJECTIVE To determine the pharmacokinetics, bioavailability, and pharmacological effects of cannabidiol (CBD) in senior horses. ANIMALS 8 university-owned senior horses. PROCEDURES In this randomized, crossover study, horses were assigned to receive either a single oral dose of 2 mg/kg CBD in oil or a single IV dose of 0.1 mg/kg CBD in DMSO between August 10 and September 4, 2020. Blood samples were collected before and then 0.5, 1, 4, 8, 24, 48, 72, 96, 120, 144, 168, 192, 216, 240, and 264 hours after CBD admin-istration. Serum biochemical analyses and CBCs were performed. Plasma concentrations of CBD and its metabolites were determined with the use of liquid chromatography-tandem mass spectrometry. RESULTS Concentrations of CBD and metabolites (7-COH CBD and 7-COOH CBD) were detected in all plasma samples up to 8 hours after dosing (oral and IV), with 7-COOH CBD being the most predominant metabolite. Pharmacokinetic results for CBD oral dosing at 2 mg/kg were mean ± SD half-life of 7.22 ± 2.86 hours, maximum concentration of 18.54 ± 9.80 ng/mL, and time to maximum concentration of 2.46 ± 1.62 hours. For both oral and IV administrations, 7-COOH CBD did not fall below the limit of quantification for the times reported. Oral bioavailability for CBD was 7.92%. There was no meaningful effect of CBD on results for CBC, serum biochemical analyses, or vital signs for any horse. CLINICAL RELEVANCE Pharmacokinetics and bioavailability of CBD in senior horses were determined, and there were no adverse effects of administering either the oral or IV dose of CBD evaluated.